nvmet_fc: add target feature flags for upcall isr contexts

Two new feature flags were added to control whether upcalls to the
transport result in context switches or stay in the calling context.

NVMET_FCTGTFEAT_CMD_IN_ISR:
  By default, if the flag is not set, the transport assumes the
  lldd is in a non-isr context and in the cpu context it should be
  for the io queue. As such, the cmd handler is called directly in the
  calling context.
  If the flag is set, indicating the upcall is an isr context, the
  transport mandates a transition to a workqueue. The workqueue assigned
  to the queue is used for the context.
NVMET_FCTGTFEAT_OPDONE_IN_ISR
  By default, if the flag is not set, the transport assumes the
  lldd is in a non-isr context and in the cpu context it should be
  for the io queue. As such, the fcp operation done callback is called
  directly in the calling context.
  If the flag is set, indicating the upcall is an isr context, the
  transport mandates a transition to a workqueue. The workqueue assigned
  to the queue is used for the context.

Updated lpfc for flags
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/target/fc.c

@@ -86,6 +86,7 @@ struct nvmet_fc_fcp_iod {
 
 	struct nvmet_req		req;
 	struct work_struct		work;
+	struct work_struct		done_work;
 
 	struct nvmet_fc_tgtport		*tgtport;
 	struct nvmet_fc_tgt_queue	*queue;
@@ -213,6 +214,7 @@ static DEFINE_IDA(nvmet_fc_tgtport_cnt);
 
 static void nvmet_fc_handle_ls_rqst_work(struct work_struct *work);
 static void nvmet_fc_handle_fcp_rqst_work(struct work_struct *work);
+static void nvmet_fc_fcp_rqst_op_done_work(struct work_struct *work);
 static void nvmet_fc_tgt_a_put(struct nvmet_fc_tgt_assoc *assoc);
 static int nvmet_fc_tgt_a_get(struct nvmet_fc_tgt_assoc *assoc);
 static void nvmet_fc_tgt_q_put(struct nvmet_fc_tgt_queue *queue);
@@ -414,6 +416,7 @@ nvmet_fc_prep_fcp_iodlist(struct nvmet_fc_tgtport *tgtport,
 
 	for (i = 0; i < queue->sqsize; fod++, i++) {
 		INIT_WORK(&fod->work, nvmet_fc_handle_fcp_rqst_work);
+		INIT_WORK(&fod->done_work, nvmet_fc_fcp_rqst_op_done_work);
 		fod->tgtport = tgtport;
 		fod->queue = queue;
 		fod->active = false;
@@ -1807,10 +1810,13 @@ nvmet_fc_transfer_fcp_data(struct nvmet_fc_tgtport *tgtport,
 	}
 }
 
+/*
+ * actual done handler for FCP operations when completed by the lldd
+ */
 static void
-nvmet_fc_xmt_fcp_op_done(struct nvmefc_tgt_fcp_req *fcpreq)
+nvmet_fc_fod_op_done(struct nvmet_fc_fcp_iod *fod)
 {
-	struct nvmet_fc_fcp_iod *fod = fcpreq->nvmet_fc_private;
+	struct nvmefc_tgt_fcp_req *fcpreq = fod->fcpreq;
 	struct nvmet_fc_tgtport *tgtport = fod->tgtport;
 	unsigned long flags;
 	bool abort;
@@ -1905,6 +1911,28 @@ nvmet_fc_xmt_fcp_op_done(struct nvmefc_tgt_fcp_req *fcpreq)
 	}
 }
 
+static void
+nvmet_fc_fcp_rqst_op_done_work(struct work_struct *work)
+{
+	struct nvmet_fc_fcp_iod *fod =
+		container_of(work, struct nvmet_fc_fcp_iod, done_work);
+
+	nvmet_fc_fod_op_done(fod);
+}
+
+static void
+nvmet_fc_xmt_fcp_op_done(struct nvmefc_tgt_fcp_req *fcpreq)
+{
+	struct nvmet_fc_fcp_iod *fod = fcpreq->nvmet_fc_private;
+	struct nvmet_fc_tgt_queue *queue = fod->queue;
+
+	if (fod->tgtport->ops->target_features & NVMET_FCTGTFEAT_OPDONE_IN_ISR)
+		/* context switch so completion is not in ISR context */
+		queue_work_on(queue->cpu, queue->work_q, &fod->done_work);
+	else
+		nvmet_fc_fod_op_done(fod);
+}
+
 /*
  * actual completion handler after execution by the nvmet layer
  */
@@ -2149,7 +2177,10 @@ nvmet_fc_rcv_fcp_req(struct nvmet_fc_target_port *target_port,
 			((queue->qid - 1) % tgtport->ops->max_hw_queues) : 0;
 	memcpy(&fod->cmdiubuf, cmdiubuf, cmdiubuf_len);
 
-	queue_work_on(queue->cpu, queue->work_q, &fod->work);
+	if (tgtport->ops->target_features & NVMET_FCTGTFEAT_CMD_IN_ISR)
+		queue_work_on(queue->cpu, queue->work_q, &fod->work);
+	else
+		nvmet_fc_handle_fcp_rqst(tgtport, fod);
 
 	return 0;
 }

drivers/nvme/target/fcloop.c

@@ -575,8 +575,9 @@ struct nvmet_fc_target_template tgttemplate = {
 	.max_dif_sgl_segments	= FCLOOP_SGL_SEGS,
 	.dma_boundary		= FCLOOP_DMABOUND_4G,
 	/* optional features */
-	.target_features	= NVMET_FCTGTFEAT_READDATA_RSP |
-				  NVMET_FCTGTFEAT_NEEDS_CMD_CPUSCHED,
+	.target_features	= NVMET_FCTGTFEAT_CMD_IN_ISR |
+				  NVMET_FCTGTFEAT_NEEDS_CMD_CPUSCHED |
+				  NVMET_FCTGTFEAT_OPDONE_IN_ISR,
 	/* sizes of additional private data for data structures */
 	.target_priv_sz		= sizeof(struct fcloop_tport),
 };

drivers/scsi/lpfc/lpfc_nvmet.c

@@ -669,7 +669,9 @@ lpfc_nvmet_create_targetport(struct lpfc_hba *phba)
 	lpfc_tgttemplate.max_hw_queues = phba->cfg_nvme_io_channel;
 	lpfc_tgttemplate.max_sgl_segments = phba->cfg_sg_seg_cnt;
 	lpfc_tgttemplate.target_features = NVMET_FCTGTFEAT_READDATA_RSP |
-					   NVMET_FCTGTFEAT_NEEDS_CMD_CPUSCHED;
+					   NVMET_FCTGTFEAT_NEEDS_CMD_CPUSCHED |
+					   NVMET_FCTGTFEAT_CMD_IN_ISR |
+					   NVMET_FCTGTFEAT_OPDONE_IN_ISR;
 
 #if (IS_ENABLED(CONFIG_NVME_TARGET_FC))
 	error = nvmet_fc_register_targetport(&pinfo, &lpfc_tgttemplate,

include/linux/nvme-fc-driver.h

@@ -655,6 +655,22 @@ enum {
 		 * on. The transport should pick a cpu to schedule the work
 		 * on.
 		 */
+	NVMET_FCTGTFEAT_CMD_IN_ISR = (1 << 2),
+		/* Bit 2: When 0, the LLDD is calling the cmd rcv handler
+		 * in a non-isr context, allowing the transport to finish
+		 * op completion in the calling context. When 1, the LLDD
+		 * is calling the cmd rcv handler in an ISR context,
+		 * requiring the transport to transition to a workqueue
+		 * for op completion.
+		 */
+	NVMET_FCTGTFEAT_OPDONE_IN_ISR = (1 << 3),
+		/* Bit 3: When 0, the LLDD is calling the op done handler
+		 * in a non-isr context, allowing the transport to finish
+		 * op completion in the calling context. When 1, the LLDD
+		 * is calling the op done handler in an ISR context,
+		 * requiring the transport to transition to a workqueue
+		 * for op completion.
+		 */
 };